Abstract: A cylinder block for a multi-cylinder engine is provided with a water jacket partly on an intake side of a row of cylinders and partly on an exhaust side of the row of cylinders and a water guide passage through which cooling water is introduced into the water jacket. The cylinder block is provided with oil return passages each of which extends straight from top to bottom of the cylinder block between each adjacent cylinders. A branch oil return passage branches off from a middle portion of the rearmost oil return passage and extends rearward up.

Abstract: A cylinder block for a multi-cylinder engine is provided with a water jacket partly on an intake side of a row of cylinders and partly on an exhaust side of the row of cylinders and a water guide passage through which cooling water is introduced into the water jacket. The cylinder block is provided with oil return passages each of which extends straight from top to bottom of the cylinder block between each adjacent cylinders. A branch oil return passage branches off from a middle portion of the rearmost oil return passage and extends rearward up.

Abstract: A cylinder block reinforcement construction for an engine includes a reinforcement member fixed to a skirt portion of a cylinder block of the half-skirt type and fastened to each of bearing caps bearing the crankshaft of the engine. The reinforcement member is formed in a platelike configuration and a substantially dishlike sectional shape and includes a bottom face portion, side face portions rising from both side ends of the bottom face portion, and flange portions provided at upper edges of the side face portions so as to be fastened to the skirt portion. The reinforcement member is provided, at positions corresponding to respective of the bearing caps and spaced in the axial direction of the crankshaft, with protuberant portions for attachment to respective of the bearing caps. The bottom face portion may be provided with bottom vent holes, each being provided between adjacent of the protuberant portions at a position corresponding to the respective cylinder.